Four years after the Dublin Port Tunnel opened, new figures show that the project ran €269m over budget from the original €535m price tag.

Documents seen by the Irish Independent show the initial budget was exceeded two years before the tunnel opened.

Audit reports commissioned by the Department of the Environment show that Dublin City Council officials, who managed the project on behalf of the National Roads Authority (NRA), were concerned as far back as September 2005 -- 15 months before the tunnel opened -- that the bill would increase.

The twin-bore tunnel opened in December 2006 after a six-year build. It was designed to bring heavy goods traffic from the M1 motorway to Dublin Port, avoiding the city centre.

The costs rose because of claims by the contractor for additional payments arising from variations in the contract, time delays and increases in the cost of materials.

The cost of securing land and property needed had also been "underestimated".

The contract for the design and construction of the tunnel was awarded to the consortium Nishimatsu Mowlem Irishenco.

The companies involved in the consortium were Nishimatsu Construction Company, a Japanese firm with extensive global tunnelling experience; Mowlem and Company, a leading UK civil engineering contractor; and Irish civil engineering contractor Irishenco Construction.

The NRA said the project ended up costing "considerably more" to build than the contractor had estimated, but that all claims for extra money were challenged.

"The contractor, in his claims, sought significantly more than what he got," a spokesman said.

Significant

"The claims were examined and contested and, as a consequence to that, there was a significant drop in the amount awarded."

He added that the increases in the tunnel's cost had resulted in a new form of contract for major road projects. A price is now agreed at the start of the contract and any extra costs have to be met by the main contractor.

Meanwhile, although the number of cars and heavy goods vehicles (HGVs) using the tunnel has increased, it is below what was expected when the 4.5km tunnel opened.

The NRA expected 21,600 vehicles a day to use it, with one in three being HGVs. But it yesterday revealed that traffic counts are running at 17,000 a day. However, this is an increase on the 14,800 vehicles that used the tunnel daily last year.